Spherical osteotomy device and Method

ABSTRACT

A spherical osteotomy device for the efficient surgical sectioning of bone includes a part spherical body and a shank. The part spherical body includes an outer surface, an inner surface, a cutting end between the outer surface and the inner surface, an axis extending from the outer surface through the inner surface, and an origin on the axis. The inner surface has a substantially constant radius extending from the origin. The shank extends outwardly from the outer surface of the body and is substantially aligned with the axis. Other embodiments of an osteotomy device are described. Also provided is a method of using the osteotomy device for performing spherical osteotomies.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.12/211,063, filed Sep. 15, 2008, pending, which claims the benefit under35 USC §119 (e) of U.S. Provisional Patent Application Ser. No.60/993,820 filed Sep. 13, 2007, the disclosure of each of which ishereby incorporated herein in its entirety by this reference.

FIELD OF INVENTION

This invention relates generally to osteotomy devices for use in thesurgical cutting of bones, and more specifically to spherical osteotomydevices for use in surgical division or sectioning of bones and a methodtherefore, particularly spherical osteotomy devices for use inperforming “true dome” osteotomies.

BACKGROUND

Osteotomy is defined as a procedure for surgical division or sectioningof a bone. Displacement osteotomy is the surgical division of a bone andshifting of the divided ends to change the alignment of the bone or toalter weight-bearing stresses. This procedure is typically utilized byorthopedic surgeons to correct for malalignment and malorientation,including uniapical and multiapical deformities of the bone, as well asthe treatment for compartmental diseases. The goal of displacementosteotomies is to create congruent matching surfaces to align,stabilize, and maximize contact between the corresponding bone sections.Osteotomies may include a number of different types of bone sectioningprocedures that result in two corresponding sections of the bone whichare then reoriented until a desired alignment between the bone sectionsis achieved. In order to improve stability, distribute the load evenly,eliminate abnormal stress, and aid healing, surgeons strive to maximizethe match or contact area between two corresponding surfaces whensurgically sectioning the bone. Representative types of bone cutsinclude simple transverse, obliqued cuneiform, stairstep, simple tocomplex wedges, barrel-vault, and dome shaped cuts. In practice, asurgeon may choose a specific cut configuration in order to achieve aparticular reconfiguration of the bone being treated.

Although so called “dome osteotomy” has been known for decades, the term“dome osteotomy” has been used to refer conventionally to semi-cylinder,i.e., half or part (partially) cylindrical, shaped surgical cuts.Specifically, amongst experts within the field, “cylindrical osteotomy”would be a more accurate descriptor for these types of so called “dome”osteotomies, as it is well understood by all to be a cylindricallyshaped cut. Although resulting shapes of so called “dome” osteotomy arenot domes, the following terms have been used in the scientificliterature to refer to osteotomies wherein corresponding bone cuts areshaped like a semi-cylinder: dome, spherical, barrel-vault, focal dome(reversed dome), crescentic, and arcuate. These conventional forms ofsemi-cylindrically shaped osteotomies are better described asbarrel-vault osteotomies, and will be described accordingly hereinbelow. Further, the term “dome osteotomy” has been used in theliterature and within the field of corrective osteotomy to describebarrel-vault osteotomy, however, the field of corrective osteotomy haslacked a method and device to accomplish, as described below withrespect to the invention herein presented, what will be termed “truedome” or spherical osteotomy.

In barrel-vault osteotomy, a bone is sectioned by oscillating a sawblade around the central axis of the cylinder while cutting the bone.Barrel-vault osteotomy may be used to correct angulation about thecentral axis of the cylindrical cut and translation along the centralaxis of the cylindrical cut. The barrel-vault osteotomy provides andallows correction in two-dimensions, which sometimes results inundesirable secondary translation because of imparted limitation oftwo-dimensional repositioning of the bone portions. In this respect,barrel-vault osteotomy cannot be used to correct axial rotations of thebone without creating gaps and instability between bone segments therebybeing a major limitation of so called “barrel-vault” osteotomies. Thesuccess of barrel-vault osteotomies relies heavily on meticulouspre-operative planning, and while it may be used to correct radialdeformities in the frontal and sagittal planes, one of its majordisadvantages is the limited ability to correct axial rotationaldeformities. Accordingly, it would be desirable to provide a devicecapable of cutting a bone into corresponding sections that allows forcorrection in more than two dimensions.

There are a variety of devices and methods available to accomplish theseso called “barrel-vault” osteotomies. One method includes drilling aseries of holes in the bone along a planned arc. In one example, U.S.Pat. No. 6,190,390 discloses an apparatus and method for the surgicalrealignment of the knee through proximal tibial osteotomy. The apparatushas an arcuate profile configuration for establishing a series ofparallel holes forming the desired semi-cylindrical contour of thebarrel-vault cut. In addition to the general disadvantages of“barrel-vault” osteotomies mentioned above, such a method undesirablycreates ridges between adjacent sets of drilled parallel holes makingalignment more difficult and gaps between bone portions more probable.

According to another example, U.S. Pat. No. 4,955,888 discloses abiradial saw blade with an arcuate body, powered by oscillating motionthat is used to create the barrel-vault osteotomy. Such saw blades aretypically associated with a saw assembly which operates to displace theblade in a reciprocating motion by oscillating the blade around thedrive axis of the saw assembly. The saw blade has a curved cutting edgeat the end of the body shaped as a part of a cylinder for makingbarrel-vault shaped surgical cuts. While the cut resulting from the useof the biradial saw blade provides for a better match of the twosurfaces of both bone portions, the heat and friction produced by thesaw blade may be detrimental to the bone, specifically for allowingproper healing thereof. Also, other conventional “barrel-vault” sawblades may include a partially cylindrically shaped body having acutting member on its leading edge.

Conventional blades are limited in providing semi-cylindrical cuts ofthe bone, which limit the correction in the bone, particularly whencorrecting deformities that lie in two planes, such as the frontal andsagittal planes. Correction of deformities in two planes requiresmeticulous preoperative planning in order to determine the central axisabout which the cut in the bone is to be made. This is especiallycrucial if the bone portions are to be properly positioned to correctthe deformity. Cutting the bone about a different central axis will onlyallow, at best, partial correction in the two planes. Further, it isdesirable to provide improvement for the correction of malalignment,malorientation and compartmental disease, including other deformities ofthe bone by osteotomy procedures and tools. Accordingly, it would bedesirable to provide an osteotomy tool for cutting bone that increasesthe adjustability of the bone portions, achieves optimal bone contact,and improves primary stability. It is also desirable to provide anosteotomy tool that is less dependent upon cutting the bone preciselyabout a determined central axis when attempting to achieve propercorrection.

Another disadvantage associated with the use of so-called “barrel-vault”osteotomies is the limited ability to correct axial rotationaldeformities. Correction of other deformities may also be difficult tomake, particularly when a correction of the deformity requires cuttingthe bone in a less accessible location. This makes it increasinglydifficult for a surgeon to provide the corrective cut, as describedabove, where it is needed. Another disadvantage of barrel-vaultosteotomies is the bone portions, after severance, may only berepositioned with respect to one another about two principal dimensions,one of the principal dimensions being an angular displacement orrotation about the central axis, and the other principal dimension beinga lateral displacement or position along the central axis. The angulardisplacement or rotation allows the bone pieces to be rotated withrespect to one another about the central axis to the desired correction.The lateral displacement or position allows the bone pieces to bepositioned with respect to each other along the central axis to thedesired correction. Also, the bone pieces may obtain the desiredcorrection through a small combination of lateral displacements andangular displacements. Lateral displacement of the bone pieces islimited to the extent that the bone portions include sufficient surfacecontact for proper healing to occur. Angular displacement of the bonepieces provides for better bone-to-bone contact than lateraldisplacement, however, angular displacement is still limited if the boneportions are to be maintained with sufficient surface contact in orderto provide for proper healing. Accordingly, it would be desirable toprovide improved osteotomy of a bone to allow for greater surfacecontact between the repositioned cut pieces. It is further desirable toprovide an osteotomy tool for severing a bone to provide correction ofthe bone pieces in more than two dimensions.

U.S. Pat. No. 5,643,270 discloses a multi-plane curvilinear saw to beused with corresponding guide, and particularly adapted for cutting thebones in a digit, and more specifically for shaping the end of a bone ina digit by ostectomy for fusion with another member of a joint in adigit. Ostectomy refers to surgical removal of a bone or part of a bone.The conventional device is specifically designed to work similarly to asurgical chisel removing cartilage and spongy bone from one side of thejoint surface. The saw blade includes a hemispherically shaped bodyhaving a flat top and a shank extending from the flat top, and a cuttingedge along an exposed edge. This conventional device provides the use ofa saw guide in order to ensure accuracy, restrict the movement of thecutting teeth to the path defined by the curved slots, and to avoidslipping of the saw and inadvertent cutting of the surrounding tissue.The saw can be delicately translated, tilted and/or rotated to a limiteddegree about the end of the bone by the surgeon to make the exact cutuntil the flat portion of the saw rests flat on the guide. The guide isa necessary component, as without it the saw would slide off the end ofthe bone. A curved shape occurs on the end of the bone, because thecutting edge with its arc is guided by a saw guide about the arcuatepath. Whereas the conventional device is advantageous for generalostectomies for shaping the end of a bone, it is impractical for preciseosteotomy of a bone. Such conventional devices undesirably require metalto metal contact between the cutting blade and the guide. Orthopedicsurgeons try to avoid contact of the saw blade with other materials(such as metal or plastic) in order to protect their instruments (avoidunnecessary wear and galling), to avoid unnecessary heat production andpotential thermal necrosis of the underlying tissue, as well as to avoidmaterial shavings getting into the open wound. Moreover, thisconventional device and method are not suitable for true domeosteotomies because, while it may create a curvilinear cut partiallyinto the bone, the device would wedge itself between opposing boneportions during the cutting process due to the shape of the sectioningelement or blade. Furthermore, the conventional device may damage thebone by creating too much pressure and heat, caused by friction, duringthe cutting procedure. Moreover, such conventional devices having a flattop on the upper end of the device restrict full cutting or sectioningof the bone into two portions, particularly when the flat top of thedevice reaches the parallel surface of the guide with respect to theaxis of the bone that prevents complete cutting of the bone.

Accordingly, it would be desirable to provide a device capable ofcutting a bone into corresponding sections resulting in a “true dome” orspherical osteotomy.

Accordingly, it is also desirable to provide an osteotomy tool andmethod for “true dome” or spherical osteotomies that result in twosubstantially congruent (one concave and one convex) surfaces aftercutting a bone.

SUMMARY OF THE INVENTION

Accordingly, the invention presented herein accomplishes a substantiallyspherical or “true dome” shape when cutting bone, facilitatingcorrection in three dimensions and aiding the healing process of the cutbones.

In embodiments of the invention, a “true dome” or spherical osteotomydevice may be used to cut a bone into two substantially mating portions,allowing correction of the bone to be accomplished by rotating boneportions about their substantially mating surfaces, which may also allowcorrection for axial rotation without unnecessary secondary translation.Moreover, “true dome” osteotomy provides for three-dimensionaladjustability of the bone while maximizing bone-to-bone surface contactand stability. Advantageously, procedures utilizing the sphericalosteotomy device require less complex pre-operative planning and providemore accurate correction.

Embodiments of the invention provide several important advantages.Specifically, a “true dome” or spherical osteotomy device, including amethod of using the spherical osteotomy device, may create dome shapedmating surfaces as opposed to semi-cylindrical cuts conventionally made,may provide for match of the proximal and distal fragments of theosteotomy, may optimize dome height, may minimize bone loss, maydecrease the complexity of pre-operative planning, may allow the surgeonto make intraoperative adjustments to attain desired correction, may notunacceptably wedge or heat bone portions during cutting, may avoidunnecessary heat and burning, may minimize damage to bone tissue and thesurrounding soft tissue, may avoid metal to metal contact of surgicalinstruments, and may aid faster and more reliable healing of the bone.Another advantage, a spherical osteotomy device may be self-guiding andself-centering within the cut being made in the bone, giving the surgeonoptions in planning the surgical approach around soft tissue structures.

In one embodiment of the invention, a spherical osteotomy device for theefficient surgical sectioning of bone is described that includes apartially spherical body and a shank. The part spherical body includesan outer surface, an inner surface, a cutting end between the outersurface and the inner surface, an axis that extends from the outersurface through the inner surface, and an origin located on the axis.The inner surface has a substantially constant radius extending from theorigin. The shank extends outwardly from the outer surface of the bodyand is substantially aligned with the axis. Optionally, the sphericalosteotomy device may be attached to an osteotome handle or to a powertool such as an oscillating saw. The spherical osteotomy may be used tocut bones or other anatomical structures into two portions in such a wayas to facilitate repositioning of oppositely opposed substantiallymating surfaces in the desired position or orientation, thereby also toaid healing.

The bone saw bit advantageously allows the bone portions after surgicalseverance to be repositioned together in at least one of three differentdegrees of motion, because the bone saw bit cuts a “true dome” osteotomyinto each bone portion. One of the bone portions will have a convexsurface that substantially mates with the other bone portion having aconcave surface. Because the surfaces have mating contours, the boneportions relatively may be rotated about the longitudinal axis of thebone and tilted in either of two dimensions about the bone to achieverepositioning in three dimensions.

Other embodiments of an osteotomy device are described.

Also provided is a method of using the osteotomy device for performing“true dome” or spherical osteotomies. The method of the instantinvention involves the following:

-   -   (1) Providing a sectioning blade of the type described herein,        wherein the sectioning blade is operably secured to a device for        oscillating the blade;    -   (2) Defining a center of rotation in the bone to be sectioned;    -   (3) Actuating the device to oscillate the blade about the origin        of the blade;    -   (4) Engaging the blade against the bone to be sectioned; and    -   (5) Sectioning the bone by passing the blade through the bone        while rotating the blade about the center of rotation.

In a preferred method the above indicated procedural steps aresupplemented by the following additional steps, namely:

-   -   (A) Defining a longitudinal axis of the bone to be sectioned;    -   (B) Defining proximal and distal longitudinal axis lines of the        bone to be sectioned;    -   (C) Finding the intersection of the proximal and distal        longitudinal axis lines, denominated as a center of rotation of        angulation (CORA);    -   (D) Generally aligning the origin of the sectioning blade with        the CORA by positioning the blade so that the origin of the        sectioning blade is at the same location as the point of        intersection—in some cases the surgeon can choose an off-set        CORA to accomplish the osteotomy;

Steps (A) through (D) are performed subsequent to step (2) above andprior to step (3) above.

In a further embodiment of the instant method, steps A-D aresupplemented by a further step (E) wherein step (E) comprises sectioningthe bone by passing the blade through the bone while rotating the bladeabout the center of rotation while retaining the origin of the bladesubstantially at the defined CORA.

Step (E) is performed simultaneously with step (5) above.

Advantageously, the osteotomy device may be utilized in a variety ofsurgical procedures beyond “true dome” or spherical osteotomies, such asbone fracture repair in humans and animals.

Other advantages, features and alternative aspects of the invention willbecome apparent when viewed in light of the detailed description of thevarious embodiments of the invention when taken in conjunction with theattached drawings and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming that which is regarded as the invention, theadvantages of this invention may be more readily ascertained from thefollowing description of the invention when read in conjunction with theaccompanying drawings in which:

FIG. 1 is a perspective view of a bone saw bit in accordance with anembodiment of the invention;

FIG. 1A is a cross sectional view of the bone saw bit of FIG. 1 takenalong section line 1A-1A;

FIG. 1B is a front view of the bone saw bit of FIG. 1;

FIG. 2 is another perspective view of the bone saw bit shown in FIG. 1;

FIG. 3 is a schematic representation illustrating a bone saw bit inaccordance with another embodiment of the invention;

FIG. 3A is a cross sectional view of the bone saw bit of FIG. 3;

FIG. 4 is a front view of the bone saw bit shown in FIG. 3;

FIG. 5 is a side view of a shank of the bone saw bit shown in FIG. 3;

FIGS. 6A-6D show various views of a pictorial representation of a bonesaw bit in accordance with yet another embodiment of the invention;

FIG. 7 is a graphical view showing dome heights in a bone for varioussized bone saw bits in accordance with embodiments of the invention;

FIGS. 8A-8E showing osteotomy of a bone using a bone saw bit inaccordance with the invention;

FIG. 9 shows two bone portions resulting from “true dome” osteotomy;

FIG. 10 is a front view of a bone saw bit of the instant invention;

FIG. 11 is a front view of an alternative bone saw bit of the invention;

FIG. 12 is a sectional side view of a bone which has been sectioned byuse of the alternative bone saw bit of FIG. 11;

FIG. 13 is a front view of a second alternative bone saw bit of theinvention;

FIG. 14 is a sectional side view of a bone which has been sectioned byuse of the second alternative bone saw bit of FIG. 12;

FIG. 15 is a perspective view of a connection structure for securing abone saw bit of the invention to an actuating device;

FIG. 15A is a perspective view of a connection element of the connectionstructure of FIG. 15 is a sectional; and

FIG. 16 is an end view of the connection structure of FIG. 15A.

DETAILED DESCRIPTION OF THE INVENTION

The illustrations presented herein are, in some instances, not actualviews of any particular osteotomy device, “true dome” osteotomy device,spherical osteotomy device, bone saw bit, cutting element, hard facingmaterial or other feature of an osteotomy bit or device, but are merelyidealized representations which are employed to describe the invention.Additionally, like elements and features among the various drawingfigures are identified for convenience with the same or similarreference numerals.

“True dome” or spherical osteotomy devices, hereinafter “bone saw bits,”suitable for osteotomy or other surgical cutting of bone are presented.Bone saw bits for surgically severing bone are now presented togetherwith some terminology to facilitate a proper understanding of theinvention.

The term “spherical” as used herein means a characteristic of a sphereover any portion of a sphere and is not to be limited to a completesphere, including, but not limited to, a hollow spherical structure.Also, the term “spherical” may refer to an inner surface, an outersurface, or an inner surface and an outer surface of a sphere, includingpartial portions thereof.

The term “part spherical” as used herein means a characteristic of asphere or a part sphere over any portion of a sphere and is not to belimited to a sphere or part sphere or a hollow sphere. Also, the term“part spherical” may refer to an inner surface, an outer surface, or aninner surface and an outer surface of a sphere or part sphere, includingpartial portions thereof.

The term “hemispherical” as used herein means a characteristic of ahemisphere over any portion of a hemisphere and is not to be limited toa hemisphere. Also, the term “hemispherical” may refer to an innersurface, an outer surface, or an inner surface and an outer surface of ahemisphere, including partial portions thereof.

As used herein the term “true dome” will be defined as a curved surface,produced by a cutting action, wherein the radius of curvature of thatcurved surface is constant or substantially constant over the entirecurved surface.

FIG. 1 is a perspective view of a device, or bone saw bit, 10 inaccordance with an embodiment of the invention. FIGS. 1A and 1B arefurther views of the bone saw bit 10. Reference may also be made to FIG.2, which shows another perspective view of the bone saw bit 10. The bonesaw bit 10 includes a part spherical body 11 and a cutting end 12, whichtogether form key features of the invention. The part spherical body 11is made of a suitably rigid material such as surgical steel, and mayinclude other materials suitable for the surgical severance of bone,particularly in aseptic environments.

The bone saw bit 10 provides for the efficient surgical sectioning ofbone (described below) and includes the part spherical body 11 having ashank 14 extending therefrom along an axis 16. The shank 14 allows thebone saw bit 10 to be attached to a chuck e.g. a three pronged chuck(not shown), of an oscillating saw (not shown). The oscillating sawrotationally drives the bone saw bit 10, as indicated by thedouble-ended arrow 15 shown in FIG. 2, to efficiently penetrate adesired member, such as bone, in order to obtain an efficient, optimalor “true” dome on both pieces of the severed member. The dome on onesevered member will result in a convex dome, while the dome on the othersevered member will result in a concave dome.

The shank 14 may have any attachment connection, such as a threaded stemor a quick release, for example without limitation. The attachmentconnection will allow the bone saw bit 10 to be attached to any device,such as a power tool or hand operated tool for improved cutting controlor usability. Also, while the shank 14 is shown as being integral withthe part spherical body 11, the shank 14 may also be a separate memberthat is coupled to the part spherical body 11. Further, the shank 14 mayinclude a hub 13 (see FIG. 2) as shown.

The part spherical body 11 also includes an outer surface 18, an innersurface 20. The cutting end 12 extends between the outer surface 18 andthe inner surface 20. The axis 16 may extend axially inline with theshank 14 and passes from the outer surface 18 through the inner surface20 of the part spherical body 11. The axis 16 includes an origin orcenter as indicated by indicia O as labeled. The inner surface 20 issubstantially characterized by having a constant radius R extending fromthe origin O Advantageously, the constant radius R allows the bone sawbit 10 to efficiently and smoothly transition over, and rotate about,the member it is cutting. Further, efficient usage of the bone saw bit10 is provided for because the outer surface 18 may also besubstantially characterized by a constant radius R′ over the substantialportion thereof, which also advantageously reduces heat generation onthe bone caused by friction while helping to prevent necrosis of thebone. Another advantage of the substantially constant radius R of theinner surface 20 and the radius R′ of the outer surface 18 is that thebone saw bit 10 is less likely to impinge upon either piece of a boneduring cutting thereby avoiding the ill healing effects caused bynecrosis.

With reference also to FIG. 3 and continued reference to FIG. 1, thecutting end 12 of the part spherical body 11 extends as an arc BDC thatlies substantially within a plane 24 intersecting the origin O. The arcBDC has a radius SR that is substantially equal to the radius “R” ofpart spherical body 11 allowing a uniform and non-complex cut to be madeby the bone saw blade 10. The radius R and radius R′ allow the partspherical body 11 to substantially follow precisely within the path madeby the cutting end 12 through the bone substantially without impingementthereupon. The dimensional difference between radius R and the radius R′is the thickness of the bone saw blade 11. While the radius SR of thearc BDC and the radius “R” are substantially equal, it is recognizedthat they may vary to a slight degree.

Optionally, the cutting end 12 may extend as an arc BDC between theouter surface 18 and the inner surface 20 of the part spherical body 11.

Returning to the bone saw bit 10 of FIG. 1, the bone saw bit 10 has apart spherical body 11. The part spherical body 11 is shaped efficientlyto allow the cutting end 12 to engage and cut through a bone atsufficiently steep angle without the bone engaging a substantial portionof the part spherical body 11 or the shank 14 as severance of the boneis completed. In other embodiments, the part spherical body 11 may becontained in less than one hemisphere, in this regard it is a partialhemispherical body. Moreover, the part spherical body 11 may have ashape substantially formed as a spherical triangle (see FIG. 6A),wherein the cutting end 12 is one of the three arcs forming thespherical triangle.

Turning again to FIG. 1, the cutting end 12 comprises a plurality ofcutting teeth 26. Each cutting tooth 26 includes oppositely opposedcutting surfaces 27, 28 arranged within a single row. It is to berecognized that other cutting teeth are contemplated within the scope ofthis invention for example, and without limitation, jagged serration,hyper- or hypo-extending surface edges and multiple rows of cuttingteeth. The opposed cutting surfaces 27, 28 of the plurality of cuttingteeth are each symmetrically spaced and aligned.

Optionally, the plurality of cutting teeth 26 may also comprise aplurality of inner cutting teeth and a plurality of outer cutting teeth,where the inner cutting teeth each have an inner tooth surface, theinner tooth surface having the radius R of the inner surface 20 of thepart spherical body 11, and the outer cutting teeth each having an outertooth surface, the outer tooth surface congruent with the outer surface18 of the part spherical body 10.

FIG. 3 shows a schematic representation, circumscribed about a sphere,illustrating a bone saw bit 10 in accordance with another embodiment ofthe invention. Reference may also be made to FIG. 4. The part sphericalbody 11 includes an outer surface 18, an inner surface 20, a cutting end12 extending between the outer surface 18 and the inner surface 20, anaxis 16 extending from the outer surface 18 through the inner surface20, and an origin O located on the axis 16. The cutting end 12 extendsas an arc BDC lying substantially within a plane 24 intersecting theorigin O. An integral shank 14 extends outwardly from the outer surface18 of the part spherical body 10 and is substantially aligned with andextends parallel to the axis 16.

The part spherical body 11 has a shape substantially formed as aspherical triangle wherein the cutting end 12 is one of the three arcsforming the spherical triangle and the other two arcs are represented bynumerals 30 and 32. As shown more specifically by FIG. 4, the sphericaltriangle is formed by a first arc defined by the cutting end 12, whichextends between vertex B and vertex C. A second arc 30 extends fromvertex B to vertex A. The third arc 32 extends from vertex A to vertexC. A cord M extends from the vertex A to the vertex B. Similarly, a cordP extends from vertex A to vertex C. In the preferred construction ofthe invention, cord M is dimensionally equivalent to cord P. A cord Textends from vertex B to vertex C. As further shown in FIG. 3, verticesB and C are each positioned at a radial distance SR from the origin O. Apoint D is defined as being positioned midway on the arc 12 extendingbetween vertices B and C. The cord T is shown as being formed of twoelements, each element being designated BR. The elements BR aredimensionally equivalent to one another. An arc m extends from thevertex A to the point D as shown in FIG. 4. A radius SR extends from theorigin O to the point D. The intersection of the radius Z, which extendsfrom the origin O to the vertex D, with the cord T defines a point G.Line Y extends from the vertex A to the point G as shown. Similarly, theline X extends from the origin O to the point G. The inner surface 20 ispositioned at a radial distance SR from the origin O. Similarly arc BDCwhich defines the cutting end of the saw bit, is also positionedsubstantially at a radial distance defined by the radius SR.

As shown in FIG. 5, the inner surface 20 of the shank 14 is alsodisposed at a radial distance corresponding to the length of the sameradius SR, which, in addition to the benefits provided herein, allowsthe bone saw bit 10 to make an efficient cut of a bone by takingadvantage of the entire part spherical body 11. As further illustratedin FIG. 5, two reference points E and H are defined at the intersectionof opposing edges of the shank 14 and the outer surface 20 of the bit11.

Advantageously as shown in FIG. 3, the alternative embodiment of thebone saw bit 11, designated bone saw bit 11A is designed for continuouscutting of a bone when the bone is equal to or smaller in diameter thanthe length of cord T or 2BR, i.e. the length of a cord between points Band C. In this particular embodiment, the length of cord T isdimensionally less than 2R where R is the length of the radius SR forthe inner surface 18 of the bit 11A a previously described. For theillustrated bit 11A, FIGS. 3 and 3A illustrate that the cutting end 12,defined along the arc BDC, lies in a plane 24 which intersects theorigin O preferentially and substantially at an angle θ from the axis16. In FIG. 3A the angle θ is shown as approximately 120 degrees. Inpreferred embodiments of the invention θ is an angle having a degreemeasure between 35 degrees and 135 degrees as measured from the axis 16.

FIGS. 6A-D show various views of a pictorial representation of a bonesaw bit 100 in accordance with yet another embodiment of the invention.The bone saw bit 100 has a part spherical body 11 that includes acutting end 12, an outer surface 18, an inner surface 20, an axis 16extending from the outer surface 18 through the inner surface 20, and anorigin O on the axis. The cutting end 12 extends between the outersurface 18 and the inner surface 20 of the part spherical body 11 andsubstantially lies within a plane 24 intersecting the axis 16. Thecutting end forms an arc BDC. The plane 24 is aligned approximately 120degrees to the axis 16 and intersects the origin O in this embodimentallowing the cutting end 12 to efficiently cut or surgically sever abone into two pieces having convex and concave domes, respectively.

Optionally, the plane 24 containing the cutting end 12 may intersect theaxis 16 at a location positioned between the origin O and the point A.Where the plane 24 intersects the axis 16 at a location between theorigin O and the point A, the radius of the cutting end 12 will have aneffective radius equal to the radius SR of the inner surface 20 of thepart spherical body 11 allowing for the same “dome” osteotomy to beperformed even though the theoretical radius is potentially smaller thanthe actual radius SR of the inner surface. To obtain the effectiveradius, a surgeon, for example, may have to rotate the saw blade bit 100about a greater circle while completing an operation (to be describedbelow). Conventional saw blades can not complete this type of “dome”osteotomy because the cutting end resides in a plane that is below theorigin which will cause, as described above, the blade to become wedgebetween the pieces of a bone being severed or cause damage theretoduring severance.

Optionally, plane 24 containing the cutting end 12 of the bone saw bit100 that intersects the axis between the origin O and the inner surface20 and may lie substantially between 35 degrees and 135 degrees from theaxis 16. While the plane 24, in this embodiment of the invention, maylie at angles greater than 135 degrees, it is expected that this to maycause undesirable binding of the bone saw bit 100 between the bonepieces being cut as described above. The plane 24 may lie with respectto the axis 16 to a lesser extent than the 35 degrees described hereinwithout consequence, but becomes less effective for cutting bones.

In still other embodiments of the invention, a plane containing thecutting end and intersecting the axis between the origin and the innersurface may be substantially perpendicular to the axis in order toachieve greater cutting surface area of a bone while making a domeosteotomy with cutting radius SR.

As with the other embodiments of the invention, the cutting end 12 mayalso comprise a plurality of cutting teeth. The cutting end 12 mayinclude other cutting structures suitable for cutting material, such asbone, as would be recognized by a person having ordinary skill in theart.

FIG. 7 shows a graphical view 200 of various dome heights 211, 213, 215,217 achieved in a bone 202 using various sized bone saw bits 210, 212,214, 216, respectively, in accordance with embodiments of the invention.

Each of the bone saw bits 210, 212, 214, 216 comprise a part sphericalbody 11 having an outer surface 18, an inner surface 20, a cutting end12 extending as an arc “BDC” between the outer surface 18 and the innersurface 20, an axis 16 extending from the outer surface 18 through theinner surface 20, and an origin O on the axis 16, the inner surface 20and the arc BDC have a radius R or SR extending from the origin O asdescribed in FIGS. 1-6.

The bone 202 includes surgically severed bone portions 203 and 204. Thebone portion 203 is a concave dome and the bone portion 204 is a convexdome. Each of the dome heights 211, 213, 215, 217 achieved by usingvarious sized bone saw bits 210, 212, 214, 216, respectively, are shownbetween the outer edges 205, 206 of the bone, but include forillustrative purpose the entire circular envelope represented by thecutting radius SR.

The dome height 211 is achieved by using the bone saw bit 210 havingradius SR that is exactly one half the width of the bone 202 and acutting end 12 that has an arc BDC. In order to sever the bone 202 intoportions 203, 204, the bone saw bit 210, while engaging the bone, isrotated about cutting center point 220. The center point 220 isrepresentative of the center point about which the bone saw bit may berotated while cutting a bone and may remain stationary or transitionwith respect to the bone depending upon the cut being made. In thisrespect, the cutting center point 220 generally denotes a floating pointabout which the tool may be rotated by a surgeon. The dome height 211 isthe theoretically largest dome height obtainable and requires precisecontrol by a surgeon in order to accomplish the osteotomy, particularlyconsidering that the cutting end may interfere with opposing boneportions and due to interference from the hub it may be difficult toaccomplish.

The dome heights 213, 215, 217, obtained by using larger more forgivingbone saw bits 212, 214, 216, range between approximately 75% and 25% ofmaximum dome height 211. However, greater or lesser dome height may beobtained by using other sized bone saw bits. Each of the bone saw bits212, 214, 216 have a cutting end 12 with an associated cord BDCsubstantially equal or greater than the diameter of the bone. As isshown in the illustration of FIG. 7, bone saw bits 212, 214, 216 areeach rotated about center points of rotation 222, 224, 226,respectively, in order to complete severance of the bone 202.

It is to be recognized that the greater the dome height, such as domeheights 211, 213, 215, 217, the greater the surface or contact area forbone portions 203 and 204 when repositioned in any of the three degreesof freedom mentioned above. Also, “true dome” osteotomies describedherein provide for the optimal contact or surface area for each boneportion 203, 204 for any given dome height.

Generally in the embodiments of the invention, the thickness of the partspherical body 11 between the inner surface 20 and the outer surface 18is mostly constant. However, it is recognized that the part sphericalbody 11 may include corrugations, ribs, cutouts or low friction coatingson or between either of the inner surface 20 and the outer surface 18 inorder to enhance the cutting efficiency of the bone saw bit or tominimize heat generation thereby minimizing necrosis of the bone.Corrugations, cutouts and ribs may act as channels for allowing acooling fluid to be directed towards the cutting end of the bone saw bitduring a surgery to further facilitate the minimization of heatgeneration. Another aspect of the bone saw bit is it will beself-guiding and self-centering while cutting bone, because of itssubstantially spherical design.

In still other embodiments of the invention, the bone saw bit mayinclude a balance member coupled to a portion of the part sphericalbody, such as the hub, and or the shank in order to balance the bone sawbit about the axis of oscillatory motion. By providing a balance member,the vibration is minimized during a cutting proceeding that facilitatesmanipulation and control of the bone saw bit by the surgeon.

It is to be recognized that the bone saw bit 10 as shown in FIG. 1includes the cutting end 12 that lies substantially in a plane thatintersects the origin O. In this regard, the cutting end 12 liessubstantially about a great circle of the bone saw bit 10, whichadvantageously allows the bone saw bit 10 to be used with an oscillatingsaw having any magnitude of oscillatory motion consistent for use withthe invention.

FIGS. 8A-E illustrates an embodiment of the instant method of performingan osteotomy of a bone 202. Initially, a bone saw bit 212 as describedabove with respect to FIG. 7 is provided. The user determines thelocation of the spherical center or origin O of the bone saw bit. Next,the user identifies a longitudinal or central axis 201 of the bone 202to be sectioned. A location 203 on the outer surface of the bone 202where the cut is to be initiated is next identified. Alternatively, theapex 223 of the anticipated cut may be identified.

Utilizing the location of the origin O relative to the cutting end 12 ofthe bone saw bit 212, i.e. the radius SR, and the location of thelongitudinal axis 201, the user calculates the location of a center ofrotation 222 for the bone saw bit 212 for the anticipated sectioning.The center of rotation is typically located at a radial distance W fromeither the location 203 or the apex 223. Radial distance W typicallycorresponds to the length of the radius SR of the bone saw bit. In manyinstances, the center of rotation 222 will be located on thelongitudinal axis 201 of the bone 202. In the embodiment of the methodshown in FIGS. 8A-E, the center of rotation 222 is positioned on thelongitudinal axis 201 at a location 207 wherein the radial distance W issubstantially identical to the length of the radius SR of the saw bit212.

Having identified the point 207 and determined the orientation of thecenter of rotation 222, the bone saw bit 212 is then positioned on thebone 202 in an orientation and angle β predetermined by the surgeon suchthat the bone saw bit 212 may be rotated as shown by arrow 230 toproduce dome height 213. In one embodiment of the invention asillustrated in FIG. 8A, the origin O of the bone saw bit is positionedat the point 207.

In this embodiment the center of rotation 222 may be determined byutilizing the methodology for determining the location of a center ofrotation of angulation as described in Principles of DeformityCorrection, New York: Springer, 2005, by Dror Paley and Contributor J.E. Herzenberg, the text of which is hereby incorporated by reference.Specific reference is made to pages 61 et seq. of the Paley book whereina method of determining a CORA (center of rotation of angulation) for adeformed bone is described. The Paley methodology utilizes avisualization of a deformed bone, which has been divided into segments.The segments are visualized as being angulated to an orientation, whichwill meet the objectives of the surgeon user. Each of the segmentsdefines a respective longitudinal axis, i.e., respectively a proximallongitudinal axis for one segment and a distal longitudinal axis for theother segment. In the visualized orientation, the pair of proximal anddistal longitudinal axes intersect and form an angle. The point at whichthe proximal and distal axis lines intersect is called the center ofrotation of angulation (CORA). In one embodiment of the method of theinstant invention, the Paley method for determining the CORA of asubject bone is utilized as a means of locating a CORA which is thenused as the center of rotation 222 for purposes of the instant method,i.e., once the location of the CORA is identified utilizing the methodof Paley the location of the CORA may be used for purposes of theinstant method by either locating the center of rotation point 222 atthe same location as the CORA or alternatively, the CORA may be utilizedto otherwise identify a location 203 or 233 at which the sectioningshould preferably be performed. Should the user adopt the latterapproach, the above described methodology may be then employed todetermine the location of the center of rotation 222.

The driver 240, an oscillating or reciprocating saw of a typeconventionally associated with surgical saws, is then energized toactuate, i.e. oscillate the cutting end of the bone saw bit 212. Thebone saw bit 212 having been positioned at the initial angle βdetermined by the surgeon relative to the center of rotation 222 suchthat the origin O of the bit is positioned on or substantially on thepoint of intersection of the center of rotation 222 and the longitudinalaxis 201 engages the bone 202 at point 203 and thereafter is rotatedabout the center of rotation 222 to cut a path (represented by the domeheight 213) by pitching or rotating the driver forward and downward.

In the embodiment of the instant method illustrated in FIGS. 8A-E, thecenter of rotation 222 remains spatially fixed throughout the procedure.

Advantageously, the surgeon will control the orientation of the saw,while the bone saw bit 212 will guide or self-guide and self centeritself while making the dome shaped cut between opposing portions 203,204 of the bone. The procedure is completed when the bone saw bit 212cuts through the bone 202. In this osteotomy example, bone saw bit 212is properly sized allowing the positional angle β at the beginning ofthe cut to be approximately 35 to 45 degrees with respect to thelongitudinal axis 201 of the bone 202, which allows the bone saw bit 212to be rotated through about 135 to 145 degrees in order to finishcutting the bone 202.

In order to balance the need for efficient cutting, the need to severthe bone in a single pass and the need to provide three dimensionaladjustment of the bone pieces, the cutting plane may intersect theorigin O at a greater or lesser angle than the 120 degrees illustratedin FIG. 8C.

FIG. 9 shows two bone portions 303, 304 of a bone 302 having “true dome”or spherical osteotomy surface having been surgically severed with a sawblade bit. Bone portion 303 includes a concave surface 305 defined bythe radius J extending from an origin L that corresponds to center ofrotation 222 and the axis 201 of the bone 303. Bone portion 304 includesa convex surface 306 defined by the radius G extending from an origin Kthat corresponds to central point 222 and the longitudinal axis 201 ofthe bone 304. It is to be recognized that the origins L and K may extendfrom a location other than the longitudinal axis 201 of the bone or thecenter of rotation 222 depending upon how the surgeon makes the cutthrough the bone with a bone saw bit. The bone 302 was severed into boneportions 303, 304 with a bone saw bit in accordance with embodiments ofthe invention as the surgeon transitioned the bone saw bit about point222 as described above.

Advantageously, the concave surface 305 substantially mates with theconvex surface 306 allowing the bone portions 303, 304 to berepositioned together about any of three degrees of freedom, because theconcave surface 305 and the convex surface 306 are both “true dome” orspherical osteotomies that substantially mate. Furthermore, the surgeonmay perform the osteotomy by positioning the central point 222, orallowing it to transition, where it is convenient to sever the bone 302,because the “true dome” or spherical osteotomy result is obtainedanywhere about the bone, particularly their central axis, when the novelbone saw bit is used.

FIGS. 10-12 illustrate an alternative embodiment of the inventionwherein the thickness of the bit 11 is altered from the bitconstructions described above. As shown in FIG. 10 a saw bit of theconstructions heretofore described has a constant thickness 307 over itsentire length. Stated otherwise, the distance between the inner surface20 and the outer surface 18 remains constant over the body of the bit.The bit shown in FIG. 11 alters this construction in that the thickness310 of the bit proximate the opposing ends 312 and 323 of the bit 11 isdimensionally larger than the thickness 311 of the bit proximate thecentral region of the bit. As shown, in this embodiment, the innersurface 20 is configured as a smooth curved surface. In thisconstruction, the radius of curvature of a location 315 on the innersurface 20 typically has a smaller radius of curvature than acorresponding location 323 on the outer surface 18 positioned along aradial line 321.

The bit 11 of FIG. 11 may be utilized in the instant invention toproduce a bone sectioning of the configuration shown in FIG. 12. Asshown a bone has been sectioned into two elements 313 and 314, utilizingthe bit of FIG. 12. The upper surface configuration of the element 313exhibits a surface which does not have a constant radius of curvatureover its entire surface. Indeed, as can be noticed, the edges 316 and317 of the upper region of the bone 313 have a much smaller radius ofcurvature than their counterpart surfaces on the sectioned portion ofbone 314. As shown in FIG. 12, the radius RR from the origin O or pointof rotation 222 is dimensionally larger than either of the radii RTwhich extend from the origin O to either of the edges of the uppersectioned end of the bone 313. This particular configuration may proveuseful in certain circumstances, notably in acute angular correctionwhere the friction between bone sections may be high enough to preventproper positioning.

FIGS. 13 and 14 illustrate a further embodiment of the invention whereinthe inner surface 20 of the bit 11 is configured to define a recess 319.In the illustrated embodiment of the bit, the thickness of the bit 11remains constant over the length of the bit with exception of the regiondefining the recess. In use the bit of FIG. 13 will produce a sectionconfiguration corresponding to FIG. 14 in which the bone element 320will define an upstanding ridge 317 and corresponding voids 326 oneither side of the ridge which separate the two bone elements from oneanother.

In acute angular correction where the friction between bone sections ishigh enough to prevent proper positioning.

FIGS. 15 and 16 illustrate a structure for interconnecting the bit 11 ofthe invention with an actuating device (not shown). The end of the bit11 is shown coupled with a connection structure which includes athreaded shaft 334 adapted for coupling with an actuating device of thetype conventionally used with surgical saws. A housing 331 defining avoid therein configured to receive a threaded element 332 is positionedon the bit 11. Element 332 defines a cavity 333 therein dimensioned toreceive a connection nut secured to the bit 11. FIG. 16 is a top view ofthe element 332.

While embodiments of the invention have been described generally withrespect to part hemispherical body, a spherical body and a sphere, it isto be recognized that a prolate or oblate spheroid shape may also beused with the teaching disclosed herein.

The bone saw bit in accordance with the embodiments described above maybe used to make “true dome” or dome-shaped cuts in solid materials, butare preferentially directed toward making dome-shaped cuts in bones,such as dome osteotomies. The bone saw bit has many applicable usesincluding osteotomy procedures in both veterinary and humanmedicine/surgery.

The saw blade bit may be provided for disposable or reusable uses andmay be available in sterile or non-sterile conditions. The saw blade bitdescribed herein is not limited to the specific applications disclosed,but may be utilized for many types of surgical procedures in humans andanimals requiring the severing, cutting or removing sections ofanatomical structures, including but not limited to: general long boneosteotomies for correction of angular deformities, resection of thediseased bone area or section between two joints of the same bone,osteotomy of bones with malunions after improper healing of fractures,osteotomy for proximal humeral deformity correction, distal humeralosteotomy for correction of cubitus varus, osteotomy of distal humerusfor correction of medial compartmental disease of the elbow, osteotomyof the distal radius for correction of premature physeal closure of theulna and/or radius, periacetabular osteotomy for the correction of hipdysplasia, proximal femural osteotomy for correction of hip dysplasiaand femural head and neck angle correction, distal femural andsupracondylar osteotomy, proximal tibial and high tibial osteotomy forunicompartmental disease correction and valgus varus correction,calcaneal osteotomy, proximal metatarsal osteotomy, Tibial PlateauLeveling Osteotomy (TPLO) etc. The saw blade bit may be of any size andpreferably constructed of stainless steel.

Generally, the invention provides a saw blade bit, and method therewith,that provides for cutting true dome shape surfaces, is self-guiding,aides healing, minimizes damage to surrounding soft tissue byself-centering, as well as provides for maximum contact of thesubstantially mating surfaces, optimal dome height, enhanced stabilityand adjustability.

The saw blade bit described above may come in different sizes andattachment configurations for use with different bone sizes and surgicalprocedures. The saw blade bit may be assembled into kits. The kits mayfurther include tools associated with the blades, such as varioushandles, screws, clamps, locking mechanisms, fastening devices,measuring devices, brackets, power tools, etc.

Also, the saw blade bit may be used to make dome shaped or substantiallyspherical cuts through solid substance.

From the foregoing the invention provides a novel device and method toperform “true dome” or spherical osteotomies. The invention attainsseveral advantages, some of which are summarized as follows: it is anadvantage of the invention to provide a device and method for making adome shaped cut through a solid substance resulting in two substantiallycongruent mating surfaces, and more specifically a device and method toperform true dome osteotomies as opposed to conventional barrel-vaultosteotomies for the purpose of correcting malalignment andmalorientation of bones in humans and animals. Another advantage of theinvention is to provide a dome saw blade and method to perform improvedcorrective osteotomies that produce two bone sections with congruentdome shaped mating surfaces that may be realigned and fixation appliedas understood by a person having skill in the art, and which may providefor optimal dome height, increased stability of the rejoined bonesections, minimized bone loss, decreased chance of damage to bone tissueand the surrounding soft tissue, rapid and structurally effectivemending or knitting of the bone, faster and more reliable healing, aswell as the orthopedic surgeon's ability to make intraoperativeadjustments to attain the desired correction, including correcting forlarge rotational deformities.

Changes may be made to the embodiments described in this disclosurewithout departing from the broad inventive concepts they illustrate.Accordingly, this invention is not limited to the particular embodimentsdisclosed, but is intended to cover all modifications that are withinthe scope of the invention as defined by the appended claims.

1.-29. (canceled)
 30. A method of using an osteotomy device forperforming spherical osteotomies, the method comprising: providing asectioning blade carried on an edge of a part spherical body, whereinthe sectioning blade is disposed at a radial distance from an origin ofsaid part spherical body, said part spherical body being operablysecured to a device for oscillating the sectioning blade; defining acenter point of rotation through the bone to be sectioned; actuating thedevice to oscillate the sectioning blade about the origin of thesectioning blade; engaging the sectioning blade against the bone to besectioned; and sectioning the bone by passing the sectioning bladethrough the bone while rotating the sectioning blade about the center ofrotation.
 31. The method of claim 30, further comprising: defining alongitudinal axis of the bone to be sectioned; defining a proximallongitudinal axis line and a distal longitudinal axis line; determiningan intersection of the proximal and distal axis lines, said intersectionbeing denominated as a center of rotation of angulation (CORA);determining a point of intersection of the CORA and the longitudinalaxis of the bone; generally aligning the origin of the sectioning bladewith the CORA and the longitudinal axis, by positioning the sectioningblade to position the origin of the sectioning blade on said CORA. 32.The method of claim 30, wherein oscillating the osteotomy device aboutits axis includes restricting oscillatory motion of the osteotomy devicewith respect to a plane containing a cutting end of the osteotomydevice.
 33. The method of claim 32, wherein the part spherical bodycomprises an outer surface, an inner surface, the cutting end extendingbetween the outer surface and the inner surface, an axis extending fromthe outer surface through the inner surface and an origin on the axis,and the inner surface and the cutting end being disposed at a radialdistance from the origin.